This invention relates to a process for the bonding of films, sheets and molded or extruded components formed from elastic and thermoplastic polymers.
The joining of molded components and films of ethylene-propylene rubber has theretofore been possible only with the aid of complicated and expensive techniques. Generally, films of ethylene-propylene rubber are joined together with adhesive strips. These adhesive strips consist, for example, of polyisobutylene, modified with bitumen and/or phenolic resins or other additives, or also of ethylene-vinyl acetate copolymers. These adhesive strips are preferably caused to begin to disssolve by means of solvents, e.g., benzine (petroleum ether), and are then pressed by rolling onto the film sections of ehtylene-propylene rubber to be bonded together.
It is also possible to effect a bond by prefabricating sheets or panels of the elastomer films into large-area covers. During the prefinishing step, the smaller sheets are joined with the aid of non-vulcanized strips and are vulcanized by the action of heat and optionally also by the action of pressure.
Both possibilities for the joining of parts of ethylene-propylene rubber, especially of unsaturated ethylene-propylene rubber, are very complicated and thus unsatisfactory. This is essentially the reason why films of ethylene-propylene rubber have been utilized heretofore only to a very minor extent.
There has thus been a need in the art for providing a usuable, simpler process suitable for the cementing of parts of elastomers as well as plastomers.
The process of this invention employs an adhesive composition comprising a mixture of atactic polyolefins. Processes are known from German Pat. No. 1,931,421, according to which viscous masses similar to the adhesives employed in this process can be produced. Also, it has been known that these masses can be utilized as lubricants having an improved viscosity characteristic, as an additive to lubricating oils to improve their viscosity, as rolling oils, as pore regulators during foam manufacture, and, in case of higher atactic proportions, as cable compounds and sealing compositions. Surprisingly, it has now been discovered that these compositions are suitable as adhesives. This property could not be predicted from the known, but basically different, practical applications of the conventional, similar masses.